This is one of my favorite routes, the paths are good and the views are spectacular once you arrive on the top off the downs looking North into the Weald basin or South towards the coast where the sea can be seen (weather permitting).
Starting out from a spacious car park the route leads up over the downs using the South downs way and looping back through a number of farms. The route is as expected quite undulating which adds an additional challenge but the last Kilometer can be used for a good PB if you are brave.
Water can be found in a number of locations though in the hotter months extra should be carried for your pooch.